Steel dowel bars have generally been used to join together and restrict concrete slabs and concrete segments in the construction and formation of concrete highways, airport runways, and other concrete structures. During the construction of concrete highways, concrete slabs are formed in sections, and adjacent concrete sections are kept in place in relation to one another using steel restraining dowel bars. These dowels bars are generally made in the form of elongated, cylindrical, high-shear rods, and they are typically made of high strength steel.
For example, in the construction of concrete roadways, multiple concrete dowel bars may be embedded between adjacent concrete slabs and may be spaced intermittently within the slabs at lateral intervals as joints between adjoining concrete slabs. These dowel bars are typically designed to permit horizontal displacement between adjacent segments of the concrete slabs, to allow movement between concrete slabs caused by thermal contraction and extraction. These dowel bars need to be as slippery as possible so that when they are placed within the concrete surrounding the dowel bars, they allow the concrete slabs to move horizontally in relation to each other. If the dowel bars do not easily slide or slip within the concrete cavity in which they reside, contractive and expansive forces caused by thermal heating and cooling will cause the concrete slabs to crack, break, and spall. Damage locally even at one steel dowel bar can cause significant damage to adjacent and nearby concrete slabs, requiring expensive and extensive repairs.
These dowel bars also keep the concrete slabs in relative uniformity against one another and restrict unwanted movement. The dowel bars prevent vertical displacement, twisting and turning, movement to the left or to the right, and rotation, between the concrete slabs, which can cause unevenness or cracking in the pavement surface. Such dowel bars, therefore, assist in maintaining a smooth top surface of the pavement, while simultaneously increasing, the strength of the concrete in the region of the joint.
Additionally, in areas where salt may be applied to a concrete roadway to reduce icing conditions, or in areas where salt may be present in sprays and mists from oceans, the concrete segments that are nearby the mist and sprays may fail, as the salt may increase and accelerate the corrosion of the steel dowel bars. Corroding steel bars, and the rust that builds up on the steel dowel bars, prevents the dowel bars from sliding back and forth within the concrete cavities that surround the dowel bars. Rusting causes steel bars to corrode and expand, resulting in up to six time its original volume. As the steel bars expand due to corrosion, friction within the concrete cavities is increased, thereby failing to allow the concrete slabs to slip and move horizontally in relation to each other. Where salt is applied to the surface of a concrete roadway to reduce the buildup of ice, or may be present in salt spray or mist from oceans, the concrete segments tend to fail quicker over time, as the salt increases corrosion of the steel dowel bars that align the segments.
Additionally, during the manufacturing of the dowel bar, enamel coating may be applied to the dowel bar in a baking process. The enamel coating is typically applied by spraying (or by other surface-application methods) an epoxy coating over the dowel bar. During the application of the enamel coating, the steel dowel bar is held along its exterior cylindrical surface. In the area where the dowel bar is held, the enamel coating will be absent, thus affecting the continuity of the application of the coating. These discontinuity areas may expose the steel dowel bar to small imperfections, scratches, chips, cracks and other flaws, and thereby degrade its integrity and resistance to corrosion and rusting. There is a need in the art for an improved process of manufacture that prevents or decreases failures caused by such manufacturing detects.
In view of the foregoing, an embodiment herein provides a method of manufacturing dowel bars that includes creating holes at disparate ends of the dowel bar to enable the insertion of pins to support and hold in place the dowel bar during the enamel coating process. An embodiment herein also provides a system comprising a dowel bar having holes at the ends of the axis of the dowel bar, end plugs inserted into such manufacturing holes, and caps attached over ends of the dowel bars.
These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.